In KMail, go to Settings -> Configure KMail -> Identities -> Modify Identity -> Cryptography -> OpenPGP Signing Key -> Choose, then select a key and click OK. Actual result: Nothing happens Expected result: Dialog is accepted and the key is assigned to the identity This is a regression from KDE 4, so it's probably caused by porting to KF5 or by behaviour change in Qt 5.
I confirm it but I don't understand why for the moment. Code is in KeySelectionDialog